Hi niko, it looks like you figured it out before I even posted!

> Is there anything else that I'm missing maybe?

No - just try to keep in mind that polygons are actually little flat faceted things and it is only through some kinds of shading tricks that they give a kind of emulation of a smooth appearance (by blending colors and/or shading normals between their vertices).

If there is some subtle variation in the vertex normals, but a relatively sparse set of polygons in that particular area (or sparse in just one direction with some skinnier polygons which is more what you were running into), the fake illusion of smoothness can be more easily broken. The solution for such things is to produce more polygons so that the illusion of smoothness holds up better.

Long and skinny polygons will have things blending between their vertices across a larger portion of the model, so they can have a tendency to make some more visible artifacts.

- Michael